Crude oil is found naturally in a mixture with water and gas. One issue that needs to be resolved immediately, when the ascending pressure is low, is the choice of the way in which it will be transported from the well head to the site where the petroleum will initially be processed. The reason for this is that it may be transported by natural, multi-phase flow, by means of multi-phase pumping (mixed with gas) or by means of pumping only the liquid component after separation of the gas phase from the petroleum. The decision in favour of one of the above-mentioned methods will depend, amongst other factors, on the characteristics of the reservoir, the characteristics of the fluids produced and environmental conditions.
One of the objectives of the present invention is to promote the efficient separation of the gas mixed with the petroleum, even on the sea bed, inside a dummy well, in such a way as to make the exploitation of certain hydrocarbon reserves located in deep ocean waters viable.
One of the principal advantages of separation on the sea bed, in a dummy well, consists in the reduction of the flow pressure of the petroleum at the bottom of the well, which permits greater recovery of the petroleum from the reservoir. The increase in production occurs because the pressure at the well head is reduced to the operating pressure of the separator, which is substantially less than the hydrostatic pressure of the depth of water or than the hydrostatic pressure of a production pipeline to the offshore platform. The separation of the stream of petroleum originating at the reservoir into two distinct streams, one of liquid and the other of gas, enables reserves to be exploited using conventional technologies which are well-known in the petroleum industry. The gas is raised by the difference in pressure between the separator and the receiving vessel located on the platform, whilst the liquid stream may be lifted, for example, using submerged centrifugal pumping (SCP) or another suitable artificial lift technique.
A further advantage of using separation on the sea bed, in the case of offshore petroleum production, lies in the possibility of saving physical space and reducing the load on the platform deck.
Yet a further significant advantage of this separation process, in connection with a natural reservoir, relates to monitoring of the reserves, since, if the flows of liquid and gas are separated, they can be measured more easily. This fact is highly significant, principally when one considers the difficulties involved in measuring a multi-phase flow. Monitoring the individual production of liquid and gas will also permit better control over production at the petroleum reservoir.
A further application of the invention, during petroleum-well drilling operations, is to the separation of gases which may be mixed with the drilling fluids.
The invention may also be applied in industry outside the area of petroleum production. In this case, restrictions of a dimensional nature are largely eliminated.